The principal is the original sum of money borrowed in a loan or invested, excluding any interest or earnings. In the context of loans, the principal is the amount that the borrower agrees to repay the lender, and interest is calculated based on this principal amount. In investments, the principal refers to the initial amount of money put into an investment, which can generate returns or earnings over time.

Importance of understanding the principal

Loan repayments

Understanding the principal is crucial for managing loan repayments. Borrowers need to know the principal amount to calculate interest payments and understand the total repayment amount over the loan term.

Interest calculation

Interest on loans and investments is often calculated based on the principal amount. Knowing the principal helps in understanding how interest accrues and affects the total cost of borrowing or the returns on an investment.

Financial planning

Understanding the principal is essential for effective financial planning. It allows individuals and businesses to budget for loan repayments, plan for investment returns, and manage their finances efficiently.

Debt reduction

Paying down the principal on a loan reduces the overall debt burden and can lead to significant interest savings over time. Strategies to reduce the principal can help borrowers become debt-free more quickly.

Investment growth

In investments, the principal is the initial amount that can grow over time through earnings or returns. Understanding the principal helps investors track the performance of their investments and assess their financial progress.

Key components of the principal

Loan principal

In a loan, the principal is the original amount borrowed that must be repaid over the term of the loan. It excludes any interest, fees, or other charges.

Investment principal

In investments, the principal is the initial amount of money invested. This principal can earn interest, dividends, or capital gains, contributing to the overall growth of the investment.

Principal balance

The principal balance is the remaining amount of the original loan principal that has not yet been repaid. As borrowers make payments, the principal balance decreases.

Principal payment

A principal payment is a payment made towards the repayment of the original loan principal, reducing the outstanding balance. Principal payments can be part of regular instalments or additional payments made to reduce the debt faster.

Pros and cons of focusing on the principal


  • Interest savings: Reducing the principal through additional payments can lead to significant interest savings over the life of the loan.
  • Debt reduction: Paying down the principal helps borrowers reduce their overall debt burden more quickly.
  • Financial clarity: Understanding the principal provides clarity on the actual amount owed or invested, aiding in better financial planning and decision-making.
  • Investment growth: In investments, a larger principal can generate more returns over time, enhancing the overall growth of the investment.


  • Initial costs: Borrowers and investors must have sufficient funds to cover the initial principal amount, which can be a significant financial commitment.
  • Opportunity cost: Using funds to pay down the principal or invest as the principal may limit the ability to use those funds for other financial goals or opportunities.
  • Fixed obligations: Loans with fixed principal amounts create regular repayment obligations, which can impact cash flow and financial flexibility.

Applications of the principal


In a mortgage, the principal is the amount borrowed to purchase a home. Borrowers make regular payments that include both principal and interest, gradually reducing the principal balance over the loan term.

Personal loans

Personal loans involve borrowing a specific principal amount that must be repaid with interest. Understanding the principal helps borrowers manage their repayments and plan their finances.

Car loans

Car loans provide funds to purchase a vehicle, with the principal being the loan amount. Borrowers repay the principal along with interest over the loan term.


In investments, the principal is the initial amount of money invested in assets such as stocks, bonds, or real estate. The principal can grow over time through earnings or returns, contributing to the investor’s wealth.

Principal in action

Consider a homeowner in Brisbane who takes out a $500,000 mortgage to purchase a property. The loan has a fixed interest rate of 4% and a term of 30 years. The key aspects of the principal in this scenario include:

  1. Loan principal: $500,000
  2. Interest rate: 4%
  3. Loan term: 30 years
  4. Monthly payments: Regular payments include both principal and interest

Each monthly payment reduces the principal balance, and additional payments towards the principal can lead to interest savings and a shorter loan term.

Connection to loans and trusts

The principal is relevant in various financial scenarios, including building loans, bridging loans, and business loans. Borrowers need to understand the principal to manage repayments and reduce their debt burden effectively. Income trusts invest in assets using a principal amount, aiming to generate returns for beneficiaries. Understanding the principal helps trustees manage investments and ensure stable returns. In all cases, knowing the principal is essential for making informed financial decisions and achieving financial goals.

Learn more

For more information on the principal and its implications, visit the Australian Securities and Investments Commission (ASIC) website.


The principal is a fundamental concept in both borrowing and investing, representing the original amount of money involved in a loan or investment. Understanding the principal is crucial for managing loan repayments, calculating interest, and planning for financial growth. By focusing on the principal, borrowers can reduce their debt burden and save on interest, while investors can track the growth of their investments. Whether in mortgages, personal loans, car loans, or investments, the principal plays a vital role in achieving financial success and stability.

DISCLAIMER: The information provided on this page is for general informational and educational purposes only and is never intended as financial advice. While we strive to ensure that the content is accurate and up-to-date, it may not reflect the most current legal or financial developments. Always consult with a qualified financial advisor or professional before making any financial decisions. Use the information at your own risk.


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